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Small Innovative Missions for Planetary Exploration

SIMPLEx_Mars_Orbiter

Project Introduction

We propose to observe Mars globally from orbit in visible and infrared wavelengths to monitor its atmosphere. This effort builds on nearly continuous observations since 1998 by MGS, followed by MRO, of nearly 16 Mars years of meteorological phenomena. Visible imaging provides infor-mation on dust and water ice cloud distribution, and IR imaging provides, through filters, temperatures of the surface and atmospheric dust (at 7.6, 9.1, and 12.1 — 1.0 μm), and at several heights in the atmosphere by "narrow" band imaging within the 15 μm atmospheric CO2 band (14.9—0.67, 15.6—0.73, and 16.0—0.77 μm). Additionally, the orbiter can act as a surface asset relay, as it carries a microProximity-1 UHF radio. Appropriate Optics focal length and Orbit altitude provide global coverage to at least 100 km above the limb, and good SNR for radio relay functions. This mission consists of seven phases: 1) EM-1 (SLS) launch to C3 = 0 cis-lunar space and a lunar flyby, 2) aphelion raise to 1.94 AU (4910 m/sec delta-V over 97 days), 3) interplanetary coast for 291 days, 4) perihelion raise to 1.54 AU (1300 m/sec delta-V over 92 days), 5) another interplanetary coast of 214 days, 6) transition to the sphere of gravitational influence of Mars (Mars rendezvous ~ 1680 m/sec delta-V over 28 days), 7) spiral down to science orbit (~1670 m/sec delta-V over 34 days) and nominal science operations. The long cruise (760 days) results from the launch delay of the EM-1 mission from 12/15/17 (an optimum time to launch for an ion-propulsion system) to 7/31/18 (a nearly worse case time to launch for any propulsion system, around opposition). Only 1 month of operations can be completed during the Program defined 5-year project limit, but the vehicle will be fully capable of completing a 1 Mars Year mission during a requested Science Enhancement Option through August 2022. The spacecraft, constrained to fit the Cubesat 6U interface, is dominated by a mission-enabling ion thruster and its single propellant volume (an Ion CAT thruster supplied by U. Michigan) that uses a eutectic metal alloy of gallium, indium and tin. Attitude control is provided by a precision miniaturized star tracker (with <1 arc min capability) and three 60 mNms reaction wheels. The single ion thruster is gimbaled to compensate for CG shifts and also to off-load reaction wheels (the third wheel axis is off-loaded by adjusting satellite roll angle and its solar panel). A radiation-tolerant spacecraft processor is used for housekeeping functions, attitude control and for payload interface and data management. The avionics system has robust SEU recovery. Two deployable and steerable 3 segment solar panels (eHawk or similar) can generate ~170 W at 1 AU at the be-ginning of the mission and ~70 W at Mars during science operations. Communication functions are provided by a S-Band receiver (with two body mounted 2π sterradian patch antennas facing in opposite directions, with one always facing towards the sun) and Ka-band transmitter (with 2.5 Watt RF output and a body-mounted ~30 dB surface-attached HGA). Science downlink supports a 116 kbps data rate during the primary science phase, which decrements slowly to 7 kbps at the worst-case Earth Mars distance. Deep-space navigation relies on standard DSN differential VLBI (∆-DOR). Spacecraft components include the: (1) thruster, its gimbal and associated electronics, (2) propellant storage, (3) attitude control (star tracker + reaction wheels, (4) telecommunications (S-up/Ka-down, (5) C&DH, 6) power system (steerable solar panel + 40 Wh battery, (6) structure + harness. Science payload consists of (i) MSSS VNIR and (ii) IR "engineering" cameras and (iii) UHF relay. The total launched satellite mass (6.7 kg propellant + 6.1 kg spacecraft) has a small amount of margin (~10%) under the 14 kg 6U specification. Malin Space Science Systems is the Prime contractor supported by Stellar Exploration.
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